It depends as much on the setting (the world) than the scenario.
One successful, fun, but not "toony" game I ran was for an Ars Modernica campaign (to make it simple, more or less a Mage-like setting).
The players had to win a competition against a team of dark fae to earn a favor from Titania. It was a game of traditional, old shinty (
http://en.wikipedia.org/wiki/Shinty).
Not to make it a simple roll contest, I planned for each round two or three events (with some daring moves from each team, some unforeseen events like a hords of magical spiders running across the field and so on). Each team was scoring points during those events - not only based on success but on how daring, acrobatics, entertaining was the actions, how much the crowd was on their side.
In between each periods (there was 3 periods in this shinty match, one during day time, one at dawn and one in the evening, altering abilities of faes, becoming more powerful), there was break where each team had to perfom in front of the fae court (with Titania or any important fae you see fit for your plot).
To transpose the learning of my game, I found out that what made it successfull was:
- ban lethal force (or make it not worth using), so there is no pressure to "kill the other before he killed me", and in fact too nasty move could be sanctionned by boo-ing of the crowd, loosing points for the team; alternatively, makes killing people really difficult - they are knocked out for a few rounds, come back to their sense and join the fray again, possibly with some malus)
- gives more weight to style than pure efficiency (giving bonus for entertaining action)
- provides plenty of props (elements of decor) that the players can use (if players ask "what is there around ?", reply "what do you want, what are you looking for ?" and make it available if it is plausible to be around).
- come prepared with sequences, small actions, tag line to keep the momentum - It is not always easy to improvise this kind of game as the rythm should be sustained.
Games where the system support specifically this kind of style:
- Dying Earth (set in Jack Vance world of Rialto the Magnificent) - for style above efficiency, for encouraging bluff and wordplay instead of swordplay
- Feng Shui - I believe PCs get malus if they keep doing the same action from one round to the next (like simply shooting, or boxing round after round) encouraging description from PC to show how different is this punch from the previous one
- Hong Kong Action Theater
Hope it helps
